Definition of the initial immunologic modifications upon in vitro gliadin challenge in the small intestine of celiac patients

Background and Aims: Mucosal cell-mediated immune response is considered the central event in the pathogenesis of celiac disease. In cultured intestinal explants from celiacs in remission, we have characterized the early stages of gliadin-induced immune activation. Methods: Intestinal biopsy specimens (15 treated celiacs and 13 controls) were cultured with gliadin or maize prolamine digests for 24 hours as well as for 1, 2, 4, 6, 8, and 12 hours in some subjects. The expression of immunologic markers was detected by immunocytochemistry. Results: Gliadin challenge may initiate two parallel pathways, one of which leads to T-cell activation and another that precedes it. Epithelial cells overexpress DR molecules after 1 hour, and in a second stage T lymphocytes become fully activated. Moreover, T lymphocytes migrate in the upper mucosal layers. T lymphocytes that migrate in the higher lamina propria compartments are mainly CD4⁺ and show markers of activation; migrating intraepithelial lymphocytes are CD8⁺ and do not express these markers. Conclusions: In vitro gliadin challenge is a suitable model to reproduce various immunologic features of celiac lesions; these may be caused by different pathways. The comprehension of these phenomena is essential to clarify the distinctive pathogenic mechanisms leading to disease and may help in defining novel therapeutical approaches.